.juzhong(@bg,@h:100px,@w){
    width: @w;
    height: @h;
    border: 1px solid black;
    color:red;
    position: absolute;
    margin: auto;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: @bg; 
}
#box{
    .juzhong(blue,300px,300px);   
    p{
        text-align: center;
    }
}
#box2{
    .juzhong(yellow,@w:200px);  
}